1989 Plymouth Sundance fire in throttle body

Tiny
FLOATY
  • MEMBER
  • 1989 PLYMOUTH SUNDANCE
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 105,000 MILES
1998 Plymouth Sundance-Had a fire in my throttle body. Burned up my Air filter (replaced), /Idle air control valve (replaced) Fuel Pressure Regulator (replaced). Took apart the throttle body and cleaned. Replaced the gaskets. Checked the fuel injector. Seems to be working/clicking. No damage to that. Gas seems to be flowing through the manifold into my tailpipe. Car cranks over. But won't start as if something is keeping it from starting. Spark plugs have spark. But seem moist. Dried them off. Put them back in after I took some sandpaper and gently cleaned off the carbon. Have also replaced the PCV Valve and elbow because there were cracks. I am @ loss as to why this won't start. Have tried to read the on board diagnostics. And all I get is battery has been reset and end of test codes. Is there some kind of relay that got tripped during the fire that is preventing the car from starting now?
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Monday, September 21st, 2015 AT 7:48 PM

7 Replies

Tiny
CARADIODOC
  • EXPERT
What caused the fire? If you have spark and fuel, the last thing you need is correct timing. If the timing belt jumped far enough, it could cause a backfire and flames shouting out of the throttle body assembly.
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Monday, September 21st, 2015 AT 9:09 PM
Tiny
FLOATY
  • MEMBER
I'm not sure what caused the fire. And i'm worried because i'm getting so much fuel into the manifold. It could happen again. I have a Holley TBI. And have been searching online. They seem to have a problem w/ flooding. Question I have is how do I know if I have something stuck open that shouldn't be?
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Tuesday, September 22nd, 2015 AT 1:15 AM
Tiny
CARADIODOC
  • EXPERT
An injector stuck open is extremely rare.

If the timing belt has jumped a few teeth, intake manifold vacuum will be lower than normal. That will be reported by the MAP sensor, and since he has the biggest say in fuel metering calculations, low vacuum equates to acceleration or heavy load, and either condition requires more fuel and is why you may see a lot of fuel spraying from the injector.

Have you checked the timing belt?
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Wednesday, September 23rd, 2015 AT 9:25 PM
Tiny
FLOATY
  • MEMBER
I didn't check the timing belt. Talked to my brother whom I bought the car from. He said he had a problem w/ the Cap and rotor. So I bought a new one just to see if that was the problem. And It now it starts. But.I'm still concerned for 2 reasons.

1. The car won't idle on it's own.

2. I've got some white smoke coming out of the tailpipe.

I think I've got some gas in the oil or still in the tailpipe.

When I give the pedal some gas. The car does seem to idle ok. No backfiring or rough idle.

It just doesn't want to idle on it's own. I replaced the Idle air control valve (got the part from a junk yard). So Is there something I need to reset for ECM to accept this part?
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Monday, October 5th, 2015 AT 6:17 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. This is going to be a hugely involved repair that is very technical. For the idle speed problem, ... I hope you're sitting down, ... Drive the car at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

The high manifold vacuum for an extended period of time is what the Engine Computer needs to see to tell it to relearn "minimum throttle" after the battery was disconnected. Until that is done, the idle speed may be too low for the engine to start unless you hold the accelerator pedal down 1/4", you won't get the nice idle flare-up to 1500 rpm at start-up, and the engine will tend to stall at stop signs.
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Monday, October 5th, 2015 AT 10:16 PM
Tiny
FLOATY
  • MEMBER
I had to go back and read this whole conversation. And noticed I made a typing error. The car is a 1989 Plymouth, Sundance. Not a 1998. So does this taking the vehicle out to the highway and running it still apply to that year?

I'm a little worried about taking this car out on a busy highway and having it stall then not restarting. How fast are we taking about "highway speeds'?
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Tuesday, October 6th, 2015 AT 3:36 AM
Tiny
CARADIODOC
  • EXPERT
'95 was the last year for the Shadow / Sundance. They were replaced by the seriously-inferior Neon.

"Highway speeds" simply means not city driving. You're over-thinking this. The Engine Computer just wants to see a steady, non-changing voltage signal from the throttle position sensor, and high intake manifold vacuum so it knows the throttle blade is closed and at its mechanical stop, not being held open by your foot. Those are the conditions the computer looks at to know the throttle is closed and it is supposed to be in control of idle speed. At that instant, it takes the reading from the throttle position sensor and puts it in memory. From then on, any time it sees that voltage, it knows it has to control idle speed.

This relearning of minimum throttle pertains to every Chrysler product with a gas engine since the early 1980s. Most people don't even notice the problem or they're unaware they unwittingly solved the stalling / hard start problem by just driving the car. All they know is the problem went away, if they noticed it at all. I have a hill near my house where I coast down it for about 40 seconds. The off-ramp from the highway nearest me allows me to coast for up to 30 seconds, so seven seconds is really very little time.

Most mechanics will do this procedure after the battery had to be disconnected if the other service requires a test-drive. Other times they should simply inform the customer of the need to do this simple final step. It may be necessary to drive with your right foot on the accelerator pedal and your left one on the brake pedal, which is how a lot of people drive anyway.
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Tuesday, October 6th, 2015 AT 6:53 PM

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